


Mine to Keep

by Catsitta



Series: Meant to be Mine [1]
Category: Undertale (Video Game)
Genre: Alternate Universe - Mobfell (Undertale), Alternate Universe - Underfell (Undertale), Bad Ending, Coercion, Collars, Gaslighting, Heavy Angst, Horror, Implied/Referenced Self-Harm, Implied/Referenced Suicide, Kidnapping, LOVE and Karma are plot relevant, M/M, Major Character Injury, Manipulation, Minor Violence, Mutilation, Non-Consensual Bondage, Possessive Behavior, Possessive Sans (Undertale), Post-Undertale Neutral Route - Leaderless Ending, Rape/Non-con Elements, References to Undertale Genocide Route, Sans (Undertale) Remembers Resets, Soulmates, Stalking, Swearing, Underfell Sans (Undertale), Undertale Monsters on the Surface, implied drugging, kustard - Freeform, non-con soul bonding
Language: English
Status: Completed
Published: 2018-10-23
Updated: 2018-10-23
Packaged: 2019-08-06 05:25:18
Rating: Mature
Warnings: Rape/Non-Con
Chapters: 1
Words: 8,962
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/16382234
Author URL: https://archiveofourown.org/users/Catsitta/pseuds/Catsitta
Summary: Sans had nothing to lose. Or so he thought. Maybe he should have given up instead of trying to finish what his old man started. There were worse things in life than passively awaiting a Reset in an Underground thick with dust.Post Leaderless Ending | Mobfell!Sans x Undertale!Sans | Dark





	Mine to Keep

**Author's Note:**

> This is a down the rabbit hole into uncomfortable themes kind of story. Not a happy fic. Lacks the fluffiness of Smoke in the Mirror. I wanted a disturbing twist on the 'soul mate’ theme and explore the darker implications of being 'destined’ or 'bonded’ to someone who has the capacity and willingness to do you harm for their own gain. Please, please, please mind the tags.

Rolling the glittering glass vial between trembling phalanges, Sans braced himself for the familiar agony he was about to subject himself to for the sake of monsterkind’s freedom. Within the innocuous tube swirled a translucent crimson substance known simply as DT. It was the purified extract of the very trait that made human souls powerful and persistent, literal liquid determination. Monsters couldn’t handle large amounts in their system. They weren’t meant to endure beyond their physical limits. One drop too much and they melted into barely cognizant amalgamations, bodies fusing with anything living nearby until their forms stabilized, no salvation from their fate.

Lucky for Sans he wasn’t a normal monster.

He filled a syringe with the contents of the vial. Hazy eyelights drifted from the needle to the scattered heaps of paper filling the tiny room. The only source of light a weakly skittering bulb, its lifespan ready to give out any day now. There was no point in delaying the inevitable. This was the last of it. The final dose of DT left in the Underground. With the human souls gone—taken? destroyed?—because of the last Fallen Child, there was no way to extract more. Failure here and now meant there were no further options left for their species. They would perish in the dark, the failing Core and faltering Hope turning to dust the last of them that remained. With no leaders and dwindling numbers, they would not last until another human fell.

This was what happened when people like him did nothing. Everyone suffered. He knew what the human was capable of, and this wasn’t the first time they silenced the Underground. There were times when the kid was even more adamant about destroying them, forcing him to act if only to make them give up. Quit. To kill them enough times that they decide genocide was too much work. Not that it mattered. That is what he told himself each time he let the kid pass by without a fight. Each time he stood the side, knowing that this Run, Papyrus would die. It would all reset anyway. Someday. Eventually. Didn’t matter that two years passed already. Time within the Barrier was a funny thing, held at the mercy, once upon a time, by a flower, and now dominated by a child that played with their lives at leisure.

Sans focused on the bared expanse of his tiba. Neat puncture wounds and precise lines marred the bone. Some were new, but most were old. His whole body was a network of little, almost invisible scars. Minute, hairline fractures healed over and forgotten. Well, save for the one stretching diagonally across his ribs. But that wasn’t the good doctor’s doing. His old man—his creator—liked to think himself above boorish brutality. So what if treated a sentient creature like an experiment for half its life? You could barely see the marks. Meant the trauma to its soul couldn’t be THAT significant. Such was the nature of intent.

It only took one hit by the human, countless resets ago, to wreck the kind of damage that followed Sans into every future iteration. 

He skimmed the point of the needle above his arm until he reached a cluster of half-healed holes. Jabbing steel into brittle bone was laughably easy. His near non-existent Hope and Defense stats made this task all the more dangerous. Sans knew he could endure it. Would endure it. He might be the literal embodiment of a glass cannon, but W.D Gaster taught him well how far his limits were. How even a monster who shouldn’t be alive, much less functional, could survive maddening abuse.

His purpose (why he was created) was to house DT within his soul without disintegrating. To be an artificial fusion of monster and human determination, capable of crossing the barrier and destroying it. The fact that Sans was finishing his old man’s work after all this time, after the Underground forgot the good doctor when he fell into the Core and Sans escaped this hell with an infant Papyrus tucked in his arms...well, it was the height of comedic irony from his perspective.

He waited passively for so long. Trapped. Helpless. Disillusioned with the idea of seeing the Surface. What harm could come of trying SOMETHING when he had nothing left to lose? If this worked, maybe, just maybe, he and the few survivors could see the sun. Or, if the notes Gaster left behind weren’t the desperate ramblings of a man lost to his insanity, he could alter the timeline himself, and prevent the barrier from ever forming.

“paps. i’m trying,” Sans mumbled as he forced the plunger down, emptying the syringe into his body. “can you forgive me for waiting so long to try?” A few seconds later, agony seized through his soul, ripping through mana lines like an electric surge. Glass shattered as it hit the tiles. He didn’t attempt to stand. Just did what he did the past few times he injected DT. Slid to the floor and laid there, prepared for the inevitable. A soul beat later and...his whole body arced, twisted, convulsed. His mouth opened with silent screams, no sound escaping as his magic was overtaken by the foreign Trait. It didn’t belong. His very being protested. Rejected. As if someone tried shoving a molten rock from Hotland into his ribcage to replace his soul. 

Sans lost track of the minutes passing. He forgot how to breathe. All reality fell away with pain as the only remnant of what was and what could be. Then, suddenly, after what could have been seconds of lifetimes, he was filled the undeniable need to wake up. To pull apart the cosmos if required. No wonder the Fallen Monsters rose when Alphys used DT on them all those years ago. With so much pure Determination burning through them, death was but a minor inconvenience. His vision returned in a blur of shapes and color. His bones felt soft and pliant, barely firmer than putty. It would take hours before they solidified properly and days before his magic flow stabilized. Heh. Maybe this would be the time that he finally blew all the breakers and jacked up his mana lines beyond repair. He knew he was damaging himself. Couldn’t create a singular bullet without nearly exploding with unformed, raw energy. Didn’t need to even summon a blaster anymore. 

Hadn’t tried.

He laid a shaking hand over his chest, gritting through the final pangs of his system ‘accepting’ the DT. His soul trying to crack but refusing. Then it was over. No more DT. No more injections. Sans laid on the floor until he found the strength to stand, mindful of his state. The singular bulb flickered, casting dizzying shadows across his cramped little laboratory. Down here, locked in the basement of his house in Snowdin, nobody would know if he dusted except his future (or is it past?) self. There may have been a time or two where he swept up his own remains from the floor after a Bad Run. What was a scientist if not constantly testing their hypotheses? Such as discovering that whether one is alive or dead when down here in this time ‘stagnant’ room, it matters not. Sentient things couldn’t unstick themselves from being reset.

Sans shuddered his way to the machine dominating the eastern wall. He ignored the essays and diagrams and glass crunching underneath slippered feet. If this plan was going to work, he might as well act before he lost the nerve...or before he realized a limit and turned into goop. Even if he couldn’t activate the machine, use his combined magic and DT to create a loop in the timeline, there was still the lingering possibility he could pass through the barrier. It would be a small matter of gathering a few human souls and then, for a short while, he could pretend he was making amends for his inaction.

Punching in a long since memorized code, the door to the machine slid open. Sans crawled inside, shut himself in, and did the one thing that no monster should do while in a state of mind such as his.

He summoned his soul.

Instead of a tiny, inverted white heart illuminating the pitch black of the machine. There was a brilliant, blinding flash before all went darker than dark. The machine worked. Using him like its own personal Core, it ripped apart the seams between time and space, dragging Sans into the Void. It was a place between all things. Neither here nor there, existing and not existenting all in a moment. He passed through this place briefly during shortcuts, aware of it like a chill whisking up the back of his neck, but never in his life had he ‘seen’ it. Experienced it. Drowned in it.

The Void wanted to keep him. Swallow him. Devour him. To pick apart his ties to reality and unthread him out of all memory. 

Sans resisted. 

Sans refused.

**Sans R E S E T.**

 

For the briefest moment, he swore he saw the gleam of a fractured star before it collapsed into supernova.

 

When he next opened his eyes, he no longer floated in the impossible darkness of the Void. Instead, he laid in a musty heap of paper, the scent of oil and smoke thick on the air. Sans knew, despite the little bare bulb having gone out, snuffing the last of the light, that he was in his basement. Exhausted, he dropped his head down onto the floor and allowed unconsciousness to consume him. 

 

Sans was vaguely aware of a voice. A gruff, thickly accented voice. Why was he hearing voices? Nobody could get in here without a key. He tried to move but his limbs were ignoring him. A single, bleary eyelight swam in a socket, trying to make sense of what he was hearing. There was light. The glow of summoned magic as opposed to electricity. Hands tugged at his clothes and limp form. 

“...how did yer…”  
“...who…”  
“wuz wrong wit…”

His soul thrummed, quivering like a trapped bird as blue magic gripped tight. Lifting instead of weighing down. Sans shivered. Cold. So cold. It was like he was plunged into a frozen lake. The time time he felt this cold it…

Sans seized. No. Nononono. Not again! LOVE. So much LOVE. Memories of fighting the human in the Judgement Hall surged into view. The scar on his rib cage burning with icy intent. He was going to die. High LV touching him. Touching his soul. Those red, red eyes. The eerie smile. Dust clinging to their clothes, skin and hair. The flash of a knife. He couldn’t dodge. Tired so tired. Cutting. Cutting. Cutting. HATE. They loathed him. Because he was an obstacle. A nuisance. Why couldn’t he just sit still like the others? Why did he cheat? Cold. He was on the floor, refusing to dust, not yet. He had to...he had to... _‘Papyrus, do you want anything from Grillby’s?’_

“...can’t have none of that.”  
“...shhh...sett...down..”  
“...relax…”

He tried to focus his magic. Judgement. Karma. He was the only one. The last one. The DT in him wouldn’t allow him to give up, to Fall, to do anything less but fight. He couldn’t dust now. Gold. So much gold. Red on gold. Birds were singing, flowers were blooming. He was in hell, the human staggering closer, more dust than flesh. He didn’t have the words for the expression on their face. _‘Papyrus...I don’t want to do this. Why do I keep having to to this?’_ Sans knew the answer to his own plea. The Judge. Not by choice, he’d have never chosen this. Asgore’s voice rumbled through a younger, smaller Sans, telling him why he felt called to the golden hallway in the castle—he was The Judge. Filling a role long since left empty. 

Karma was a rare gift. One that cared not about bloodlines or physical strength. There were stories about why it existed, a way of keeping peace and balance, the perfect punishments always dealt for the crime. A counterbalance to the monarchy. An advisor and defender. The Judge didn’t need to have high attack, it couldn’t harm those without LV, and hit harder the more sins its opponent bore. Karma was The Judge’s FIGHT as well as their MERCY. 

No matter how pointless it was to try to stop the kid, it was just as pointless to resist his inherent nature. The Judge would always stand in the face of a foe when Karma decreed an execution. (He wasn’t a killer, he wasn’t he wasn’t he wasn’t.) 

“fuck, yer stats...how aint yer…”  
“this is fer yer own good.”

Sans reached for the void. For a blaster. For an escape. For relief. For anything. But his overexerted magic was a trickle down abused mana lines. He was being held together by sheer determination and what remained of depleted reserves. The cold crept deeper. Smothered. Numbed. Overwhelmed. Slowly, the golden Judgement Hall fell away, replaced by a sea of disordered shapes and sounds. Instead of screaming threatening profanities or whispering of merciless plots of murder, the LV-tainted intent of the magic encompassing his soul was calming. In the same way as a chloroform-soaked pillow made of bricks to the face was calming. It hit hard, fast and you were on the ground unconscious before you could think about tensing up.

“there yer go, sweetheart. just go to sleep. yer gonna be treated real nice and safe now.”

Sans took in one last desperate breath before he slipped beneath the churning, obsidian surface of a sea named slumber.

 

“beautiful.”

Sans wasn’t sure how long he was asleep, but he woke to the sound of that voice from earlier and the clatter of metal. Eyelights forming properly in aching sockets, magic stable enough for the moment, he took his first good look at the speaker. Or tried to. His vision was nothing but black. Heh. Hehe. Did he...did he finally screw up so badly that he blinded himself? His magic flow remained strangled on fried mana lines, so it was possible that this was just a temporary infliction. Sans reached to rub at his sockets, as if doing so would return his sight, only to meet cloth. His eyes were covered. He wasn’t blind. Thank Angel! But that led to a different problem. Where was he and why did this individual blindfold him? Sans tried to sit up, his efforts thwarted by a hand pinning him down by his sternum, pushing him into what felt like a mattress instead of the floor.

“easy, dollface, easy. don’ go excitin’ yerself.” Whoever this monster was, they sounded male, their baritone gravely, words slow and half-slurred like he couldn’t be bothered to finish them. “yer just gonna pass out ‘gain if yer don’t stay layin’ down. surprised yer even conscious now tiba honest.” The monster chuckled at his word play, thumb scraping against the exposed bone of Sans’ sternum. Wait. Exposed bone. Where was his shirt? He never let anyone see him without a shirt! That scar. No monster with stats like his should be able to have scars, much less one that looked like he was nearly bisected by a blade of pure hate.

He grabbed at his magic, at his determination, at anything he could summon up to get this monster away. Away from the scar. Away from—

_FailureShamePainDeath_

—him.

Frigid intent slammed into Sans, the blizzard snuffing out the sputtering candle of Sans’ own. Domineering. Powerful. Controlling. If he had to guess, this monster has magic potential and reserves similar to his own (well, like his when he hadn’t messed himself up with DT). He shivered against the cold permeating his bones from the inside out. The LV this guy had was revolting. Not nearly as high as the kid on their last Run, but enough to warp his magic, reveal that he didn’t simply have an accident or two where he needed to defend himself and something went bad. No, the monster was a murderer. A murderer that somehow ended up in his basement lab and was now had him at his mercy.

If he wasn’t so numbed out, he’d be panicking right now. Downside of high levels of DT, it made you give a shit about living. 

“so skittish. someone hurt yer real bad, didn’t they, sweetheart? don’tcha worry no more. aint nobody gonna take yer away from me, not after yer worked so hard to find me, and if yer good and lemme treat yer nice, yer won’t want fer nuthin’. how’s that sound?”

It sounded terrifying. Clawed fingers slid from his sternum to wrap around Sans’ wrists, guiding his hands away from the blindfold towards either side of his head. Dipping into newfound pools of determination, he drew a knee up and kicked at his captor. A bare foot planted against what felt like clothed hip bones, the other monster’s grip loosening.

_**“l e t m e g o.”**_

His magic may be muted by suffocated mana lines, but he still had Karma. All he needed to muster up was the tiniest bit with the right intent, and this monster would learn that he wasn’t all that his stats made him out to be. He might just explode while doing so, but small details. If he survived the backlash, then he could try to figure out if his shortcuts still worked or if they’d dump him back into the Void.

Finally, he felt it. A spark. He tugged and tugged until there was the sensation of a construct forming...only to be replaced by a pulse ripping through his bones. His lacking reserves were probably the only thing that stopped him bursting, the DT giving him enough basic self-preservation that he didn’t rip himself apart to supply the attack. However, it was enough to make the other monster rip his hands away as if burned.

Sans sat up and groped for the blindfold, startled when the room filled with laughter. “i dun believe it, yer really are perfect,” the stranger said. “fuck, i could jus’ collar yer right now. fact, think i will.” The fabric fell away and Sans found himself face to face with what was best described as his evil clone. Red eyelights gleamed in narrowed sockets, pointed teeth twisted in a predatory grin, and he was dressed in unrelieved crimson-and-black. He looked like a gangster out of one of those Surface movies that sometimes washed into the Dump.

The red-eyed skeleton stepped closer, the rattle of metal drawing Sans’ gaze to his hands. In sharped phalanges was a dog collar, like he saw canine couples wear, a length of chain like a leash secured to the front. “yer neck will look so pretty wrapped in leather.” Deciding that this was officially a ‘fuck no, I’m out’ moment, Sans rolled off the mattress, at last registering that he had no idea where he was right now, beyond it was not his lab. He assumed it was the monster’s bedroom, given what he could distinguish in the dim lighting.

There was a window behind him, blocked off by thick curtains, and a shut door right ahead. Beneath his feet he felt fabric and the crunch of paper, reminding him of the abandoned socks and other debris that littered his own room. No point in cleaning up when there was no one to notice or care. No younger brother to harp about his laziness or to bribe him to eat when the exhaustion caught up with him.

Sans bolted for the door, ignoring the way his bones screamed against the action. Void magic had its quirks. Shortcuts were easier to make when passing through an entryway, or around a corner. Even walking into a closet and shutting the door was sometimes enough of a transition. The mind often got in the way of magic. By crossing a threshold, it was easier to perceive himself entering a new location, the little rips in the fabric of space less fluid in his grip. Without these transitions, it was far harder to move his physical form, and the results were mixed. 

He yanked the door open and threw himself into the hall. Sans staggered, struggling to keep on his feet. Okay, nope, no shortcuts right now. He forced himself to keep moving, nearly fumbling down a flight of stairs. His vision was focused, one objective clear. The front door was in sight. Sans wasn’t sure what he’d do once he escaped since he was already fatigued, but at least he had more options. He pulled open the door and—

Stopped.

Light poured over him. Bright, blinding light. He knew its name from the scant few Resets where the human child was peaceful. Above him raining bright was the sun. But...that meant he was on the Surface. How did he get to the Surface?

“why yer actin’ like yer never seen the outside ‘fore?” asked the red-eyed skeleton. Sans jolted. His captor stood in front of him, hands tucked into the pockets of his trousers. A golden false tooth gleamed in the light. Amusement shifted into a foreboding lecherousness. “don’ worry dollface, i’ll forgive this lil’ slip up. obvious yer hurt and confused and didn’t mean to disrespect yer master like that. all’s yer hafta to is apologize real sweet. mebbe gimmie a kiss fer not punishin’ yer like i should.” 

Master? Apologize? Kiss?! 

Sans opened his mouth to retaliate, but the other skeleton silenced his protests before they could begin, wrapping claws around his neck and slamming the door behind them both. “be careful what’cha do next, pet,” he said, the warning airy. “i wanna treat yer nice.” Meeting those red-eyelights, Sans opened up with vision with a CHECK. 

 

Sans  
LV 7 | HP 10/5 | ATK 1 | DEF 1  
*It’s you

 

While the LV was lower than he assumed, it was the flavor text that made his non-existent gut roll. His thoughts skipped to the machine, to Gaster’s theories, to the resets. “the barrier...what happened to the barrier?” Sans curled his finger around the other skeleton’s wrist. The red Sans—Red, he’d call him for now—lifted his browbones.

“barrier been gone fer two years now,” he said dismissively, as if it was a taboo to be ignored instead of discussed. “now ‘bout that apology.” A pointed thumb slid across his cervical vertebrae. Sans’ whole body went slack, unresisting as he contemplated what he’d done. Had he altered his timeline? Did he somehow create a divergent timeline? Was this even his timeline at all? This Sans—Red—was him. But a him with LV (how did he gain LV?) and a home on the Surface. A him with frostbitten magic and a twisted perversion. “heh, not quite what i wuz lookin’ fer, but it’s only yer first day. yer’ll learn.” 

Before Sans could come back into himself, shark-like teeth were jammed against his, a frigid tentacle of a tongue forcing into his mouth. It was disgusting! Slick and slimy. Too weak to properly fight back, he did the one thing that came to mind. He bit down. Not exactly the safest or brightest action given the hand around his throat. A hand that immediately clamped down, digging into brittle bone so tightly that his single HP shivered in anticipation. Red swung him into a wall, knocking his skull with an audible crack. It should hurt more. He should be fighting more. But he was so tired...so very, very tired. 

“tsk. twice now yer attacked me. do that ‘gain and yer won’t like what happens next, dollface.”

He couldn’t form a construct. He couldn’t shortcut. He could barely keep conscious. He would later blame it on the DT when his smile widened and he spat the slime from Red’s tongue into the other skeleton’s face. Crimson eyelights blacked out.

So did Sans.

 

It could have been minutes, hours or days later, but when Sans woke, he woke with a gasp and a choke, a pang of terrible wrongness (invasiveness) ripping him out of the otherwise blissful lull of nothing. The blindfold was back, blocking out his vision, but he was hyper aware of someone touching him. Not his body, but HIM. His very self. His soul. He wanted to FIGHT (to flee) to do whatever it took to put his soul back behind his ribs, but he couldn’t move. There was an unfamiliar pressure around his neck (don’t be a collar, don’t be a collar) and what felt like rope was tied between both of his ulna and radius. If his legs were bound as well, Sans couldn’t tell, because someone—Red, it had to be Red—was straddling them. 

What kind of demented pervert ties up another monster and fucking fondles their soul?! 

“shh, yer like a scared little baby bird in my hand,” Red murmured. “all i’d hafta do is squeeze and you’d be dead in a second.” 

Why was he doing this? Why him? Why now?

“i realized sumthin’ while yer wuz out. yer were too busy bein’ spooked and fightin’ to hear what yer soul’s been singing this whole time.” Red rubbed the edge of Sans’ soul, answering the unspoken questions, lingering where Sans knew there was a hairline fracture. A crack that would never heal. Souls weren’t supposed to be handled like this. It was _wrongwrongwrong_. He could so easily kill him (cause him agony) with too rough a touch and not enough positive intent. Soul touching was private, only done by oneself, or between two monsters that trusted each other deeply. “yer mine. only mine. mine to protect, mine to love, mine to keep. all mine. like destiny.”

Ugly possessiveness swept through Sans, greedy and ravenous. 

“you’ll know what i mean in a moment. jus’ relax. then we can move past all this fightin’ nonsense.”

_No. No. Nonononono!_

Sans thrashed, trying to dislodge his captor, trying to delve into his magic, into his determination...trying anything at all. Suddenly, it was like he was injected with liquid nitrogen. A scream tore free as his very being was violated by...by....

His soulmate?

The word tasted of bitterness and betrayal. A final fuck you from the universe that seemed to take so much enjoyment out of his suffering. Soulmate was a term used for the phenomena of two souls sharing a harmony. It didn’t mean two monsters were destined lovers, but it occurred so rarely that is was romanticized as the ultimate ideal. Why, one might ask? Because when two souls shared a harmony, they were stupidly easy to create a bond between. Getting too cuddly with your soulmate was potentially enough for them to adhere to one another and blaze a connection. There was no need to spend time learning to love and trust another monster enough that your souls wouldn’t recoil. They were already singing the same tune, perceiving the other soul as itself. Not as a missing half, but literally, itself.

Despite their obvious differences, Red was him at the core.

Sans inhaled deeply, realizing that he wasn’t in pain anymore. Nor was he numb like when Red smothered him with Intent. He was eerily at ease, his whole body an ebbing ocean without a storm in sight. One might even dare call the sensation pleasant. Floating and full. Karma should be ripping them apart, but...it wasn’t.

“that’s ‘cause yer not the only one with that kinda magic,” Red replied, seeding more questions than answers. Sans couldn’t tell if it was spoken aloud or simply his soul speaking to his. Through his. Through the fledgling threads of a bond ready to flourish into existence. “yer’’ll understand soon.”

“please, stop. don’t do this.”

Red had to feel his fear and revulsion, because Sans was immersed in his doppelgangers’ covetous obsession. It was impossible to ignore the urgent want to bind, to hold, to own. 

“if i don’t, you’ll jus’ leave, won’tcha pet?” he said. Like everyone else. Sans felt a wash of lust so decadent that it could be dipped in chocolate, “oh, would yer look at that. we look good together.” Their souls. He was looking at their souls overlapping, glowing, singing. It would be simple to fall apart, to submit to the pleasure such an act brought upon him. Sans shuddered, choking on desire that was not his own. That was unwanted. 

Like a river flooding past its banks, sweeping aside barriers and bridges until all was in ruin, their souls Forged. For a moment, they were one, memories colliding and melding.

 

.

 

Sans watched the human child spare Boss. Confusion twisted into hatred. None of the monsters deserved MERCY. Not that pitiful flower they carried around. Nor his own brother. The human was supposed to lay waste to the souls here, cleanse them of their sins by rendering them dust. Yet here they were, attempting to redeem one of the coldest bastards in the Underground. Papyrus—Boss—was Vice Captain of the Royal Guard. The number of deaths sitting on his shoulders was on par with a select few. He enjoyed hurting others and rested on that precarious edge between sadism and insanity.

If the kid tore off the skeleton’s head, it would be justice served.

 

Across from him stood the stupid, confounding human. They made it to the Judgement Hall, battered but alive. Here they were trying to convince him to let them pass so they could talk to Asgore. How all they wanted to do was help the monsters. That they would break the barrier so they could be free. Sans laughed in their face.

“I don’t get you kid,” he sneered. A ring of blasters formed around them. “You were supposed to kill us all.” The room lit up from the blasts. He felt Karma lurk, unable to harm an innocent. It wouldn’t be happy with anything less than annihilation. The Law was that way for a reason. What kind of Judge would he be if he let this thwarted execution go unpunished? 

This world wasn’t salvageable. 

 

When Sans was a child, his very being reviled LOVE. It made him nervous, fearful. Monsters would want him dead if they knew that his meager stats meant little when Karma hit according to their LV. They already preyed on him for being 1HP. Only his father’s presence kept him safe. But it became evident that he saw this trait as a threat, something to be snuffed out. No one knew much about how Karma worked, but the royal scientist believed he knew the fix. One couldn’t be The Judge if they were guilty of the very act that their soul condemned. Right? The first Execution Points were like acid, forced upon him by Gaster overloading his magic while another monster was in the room. 

The next were much the same.

He had two levels when his old man fell into the Core. Sans fucked right out of there, smashing everything he could find on the way out. To his surprise, he found a younger skeleton in a cell, near feral as he slunk from one side to the other. Pity that he didn’t know how much Gaster screwed up his head, or he would have left the brat in there to dust instead of rescuing him.

 

Killing was easy. There were so many monsters corrupted by violence. If they were stupid enough to cross him, he’d be their executioner. It’s what they deserved. 

 

The king had six human souls. Sans had six levels. The Judge had no MERCY to spare, corrupted by a society that sought no redemption. Karma whispered. Humans were far stronger than monsters. One was capable of dusting even the strongest amongst them with a single blow. There would be no seventh soul. No broken barrier. Only Justice. Once the Underground was empty, the human could go free, this The Judge decreed.

 

Sans stared at the human, exhausted, barely able to stay awake. Blood dripped from the human’s arm, there was a smear across their face. The amount of hope in their eyes was sickening. Who were they to forgive him? To spare him? They were supposed to kill him! They were supposed to walk into the Hall coated in grey. He wouldn’t have stopped them if they tried to kill him. He’d have stood there and let it happen!

“Don’t worry, I will make everything right,” the child said, running past to where Asgore waited.

This wouldn’t do. Couldn’t…

 

“What do I have to do?”

The kid was literally begging him for monsterkind’s freedom. They spared everyone. Including the King. Only Sans stood in their way. The Judge considered their plea and offered a bargain. 

“yer life fer theirs.”

Sans knew about the Resets. The Saves and Loads. He was asking for the kid to stay dead. Only if their determination to save these worthless souls was greater than their determination to live would he allow them to pass. If they reloaded and tried again, he wouldn’t offer this deal a second time. 

 

Two years on the Surface, monsters and humans proved they could barely tolerate each other. Sans decided he liked standing on the sidelines, watching the evils of the world try to destroy each other over money and fear. Smuggling booze for the humans was an easy paycheck. Abducting a kidnapper for the monsters was almost fun. Ebott City was a crime-ridden city in the midst of an economic depression when the barrier broke. The monsters integrated seamlessly—falling back into old habits without their ‘savior’ to beg mercy of them. 

It was the anniversary of the kid’s sacrifice. Good as time as any to check on their soul. He took a shortcut to his house Underground. The traps maintained to keep scavengers out. He went into the basement, planning on taking a gander at that red soul in a jar, before blipping back to the Surface, when he realized that he wasn’t alone. The room reeked of machinery and laying on the floor was a skeleton monster. There were no other skeletons aside from him and Boss. Did...did he possibly miss one of Gaster’s experiments? He created a small glow in his palm and tugged at the monster’s strange attire.

“how did yer get in here? i’m the only one wit a key and there’s no way to ‘port in here...made sure of that. who are you?” He CHECKED the skeleton, started by the utter gibberish that he received in return. “wuz wrong wit yer stats?” He grabbed the skeleton with blue magic, deeming it the safest way to handle the stranger. Suddenly, the other skeleton was in the midst of a seizure, desperation and fear as evident as his magical fatigue.

Sans felt an echo in his core. Funny. Well, letting this monster dust wasn’t going to garner any answers. It had been a long time since he tried to comfort anyone.

“we can’t have none of that tossin’ and fightin’.” Nothing. “Urg, shhh, yer gotta settle down, and try to relax or yer’ll crack yer own damned skull.” Again, there was a pang in his soul, something dangerously close to empathy. All monsters were damned by design. Sans dared another CHECK. 

 

Sans  
LV 1 | HP .5/1 | ATK 1 | DEF 1  
*It’s you

 

“fuck, yer stats are shit. how did yer hp git into fractions? how aint yer dust?” Sans paused as he considered the level and the flavor text. The singing suddenly making an alarming amount of sense. His soul crooned, reveling in the kinship of a shared melody. No LOVE and so very vulnerable, his being yearning for understanding. For a purpose. But it was afraid. Even of its twin. Fearful of the cold promise his magic bore. Aware that if he did nothing about the rising panic in the monster, he could Fall Down right here, Sans flared his aura, quelled the sparking, sputtering fire of fear with intent. “this is fer yer own good.”

Sweat crept down the back of Sans’ neck when the other monster started to calm, too weak to properly fight. He looked...beautiful in his defeat. “there yer go, sweetheart. just go to sleep. yer gonna be treated real nice and safe now.” His soul pulsed with a note akin to adoration. This precious creature was his now. It mattered not where he came from, because he was here and in Sans’ arms. He was warm. How long had it been since he felt warm?

 

.

 

The memories fell away as their souls parted, returning to the safety of ribcages, leaving Sans to collect himself in the aftermath. He knew Red. And Red knew Sans. A moment of unparalleled intimacy tarnished beyond salvation. They would always be aware of the other, short of one of their harmonies falling out of synch, a blizzard and a wildfire entwined and unable (unwilling) to suffocate the other.

Red slid a hand across Sans’ sternum and his ribs, a groan escaping him, “don’ worry, there aint no more resets. made sure of that.”

No more resets. Heh. Hehe. That meant that if he dusted, he’d stay dead. It meant that wasn’t going to see Papyrus again. It meant he both succeeded and failed on every level to accomplish what he wanted when injecting himself with DT. This world was without a barrier, but it was warped and wrong. He curled his hands into fists. For the first time since arriving here, he felt...whole. A side effect of the soul sharing—raw energy from Red’s soul now flowed through his bones like electricity through a rusted wire. His permanent grin twisted as he reached into his half-filled reserves and pulled. The air heated and hummed.

“fuckin’ hell!” Red threw himself off of Sans, narrowly dodging the burst of raw energy. His mana lines might be ruined, his magic hard to refine, but ironically, the sorta exploding thing was just what Sans wanted. Steel and rope gave way, allowing him to roll onto his knees and rip the blindfold off. They were back in his bedroom. Without hesitating, he grabbed Red’s soul with blue magic and tossed the asshole into a couple walls, before outright chucking him through the window with a crash. That soul bond wouldn’t allow him dust Red without dusting himself (because a rent like that would be too much strain on his singular HP) but knocking him around a bit was a perfectly valid option. Especially since he needed Red distracted if he was going to escape.

A long, drawn out fight was the opposite of a good idea. His strength was better used to run and formulate a way out of this mess. (A way back to his miserable, broken timeline.)

Sans bolted for the door, outright blissful when he stepped through the Void.

 

Running from one’s soulmate was not an easy feat—bonded souls preferred closeness. It physically hurt to remain distant or to hate them. Monsters were not naturally inclined towards hate. Luckily Sans wasn’t a normal monster. That’s what he told himself when he injected the DT and that’s what he kept telling himself as he ‘ported across the Underground in search of his next hiding spot, spurned onwards by an unnatural willfulness. A part of him wanted to curl up in a hole, claw open his ribs until this forsaken bond disappeared. A different part twisted into his throat, whispering, mocking, about how he felt pleasure from his own violation, asked why he didn’t fight harder, why he hesitated, how it was his fault that this happened. If he had just waited for the kid to reset. If he hadn’t let the kid empty the underground. If he had given up earlier or given a damn when it mattered.

Blame and guilt, however, were shoved into the smallest box in his brain he could find, survival overtaking self-loathing. He pretended that the pink in the water when he found time to bathe was from scrubbing too hard. 

There was no way to shortcut into the basement in order to scour it for resources or even grab the human soul. True lab was a good alternative, and where Sans ended up whenever he felt safe enough to work on a new cross-dimensional travel machine. Parts were gathered from the dump, and schematics pulled from memory, while hours were poured into rebuilding the device that landed him in this hellhole. However, there were a few kinks in his little plan. The first being that he couldn’t stay too long in one place or Red would be able to find him (Sans didn’t know the Above at all, and couldn’t shortcut his way anywhere but Red’s room, a place he did not want to be) and the second being he needed more DT. 

His last trip stripped him of a good deal of it, and while he held more than some humans in his soul, he wasn’t going to be get anywhere unless he had more. He couldn’t just be determined. He had to be determined enough to defy the laws of magic, space, time and nature. This meant he needed access to a human soul and the Extractor. Sans assumed Alphys had the machine somewhere on the Surface, and of course, that was where all the humans were too.

Sans ignored the ache in his chest and steeled himself for the next shortcut. Red was Underground today. That meant constantly looking over his shoulder and hoping that the other skeleton didn’t figure out the location of the machine.

 

His first trips to the Surface were brief. Sans surveyed Ebbot City with his back to a wall, keeping out of sight. It wasn’t long before he realized how badly he stuck out, his clothes all wrong, his LV too low. Stealing wasn’t exactly right, but his hoodie was both unusual and falling apart. The shirt and trousers fit poorly, but they were clean. A few visits after he changed into his new attire, he slipped into a restaurant marked ‘monsters only’, the allure of a hot meal too great to resist, especially when he had some loose change tucked in a pocket, skimmed from the streets outside of wealthier looking establishments.

A purple fire elemental worked behind the counter, reminding him of Grillby so greatly that Sans wanted to grab him into a hug. He didn’t do that. Instead he sauntered his way to a seat and ordered a bottle of ketchup and whatever was hot off the grill. The elemental stared at him for a long, disturbing minute, before complying, as if he were trying to piece together a complicated puzzle. 

Sans made a habit of returning when he could find the cash.

It was here that he learned a few interesting details about the Surface...and Red. 

“You hear ‘bout the skeleton brothers raiding that warehouse off Main?”

“That was them? Heard that there was a big blow out between two of the mafia’s in town.”

“Little birdie on the street told me that the Marigolds got greedy and tried to go back on a deal. The Dreemurs sent the brothers out to make sure they knew who the top dogs are in town. Nobody messes with them and gets away with it.”

“Guess even money will get lazy shits like Sans to do some real work.”

“Shhh. Keep your voice down. He might not be a Dreemer but the Family won’t like you talking about him like that. And if word gets back to him…”

Most of what he heard ran along the same vein. Raids, fights, thefts and smuggling. Red didn’t seem to care who paid him. His relationship with his brother was obviously a tense affair, with the pair often seen arguing if they weren’t working a job together. 

 

“the usual,” Sans told Grillby—despite being purple with a metric ton of LV, he was a version of his old friend. It had been a month since he started coming here. The elemental asked no questions, simply served him and waited for Sans to scarf down his meal. Loitering was asking for troubles. Like always, Grillby laid a bottle of ketchup in front of him before going to the kitchen to place his order with the cook. 

Sans sipped the glorious red nectar, daring to relax a little. He half expected monsters to pick fights with him everywhere he went, but aside from a few crude remarks about what they could do together in the bedroom when they saw his stats, they left him alone. 

Sans yawned. Hm. Grillby was talking longer than normal to come back. Maybe there was an issue in the kitchen. He rubbed his sockets, the heaviness of fatigue dragging at his bones. When was the last time he had a proper night’s sleep? He took another sip, but found the bottle empty. Weird. Sans folded his arms on the counter and set his chin down, shoulders dropping as he soaked up the warmth of the fire elemental’s establishment, the oppressive chill of LV ignorable. If he shut his eyes he could pretend that he was back at home, dozing at the bar, and Papyrus would barge through the door any moment to drag him away. He’d get a scolding, then he’d read Peek-a-boo With Fluffy Bunny to Paps, and they’d go to bed like normal. No soulmates to run from. No human children to fight. Just him and his bro. 

_‘i know i’ve asked this before, but can you forgive me paps? i’m trying. i haven’t given up. i’ve wanted to, but i haven’t.’_

The door to the restaurant opened and a hush fell over the room. Maybe a police officer walked in. They liked to investigate monster establishments for illegal activity, such as serving alcohol or selling contraband. Sometimes they’d frisk monsters in search of weapons. It was rare for monsters to bother with human firearms, but apparently the mobster types liked their guns.

Heavy footsteps approached and then the stool next to Sans squeaked. 

“thanks grillbz fer takin’ good care of ‘im fer me. i’ll take it from here.”

Sans jolted. He almost fell from his seat when Red grabbed the back of his neck. Why didn’t he notice Red approaching? Why was the world all blurry? Why could he barely move? The other skeleton hauled Sans to face him, a second gold tooth flashing in his smile, new and shiny. “i’mma make a few things clear, dollface. only reason yer not dead is ‘cause of me. everyone in this room would have gone fer your pretty little bones if i didn’t have a claim. ol’ grillbz here been keepin’ an eye on yer ‘cause i asked, made sure yer wuz fed up and safe when yer came in. knew yer couldn’t resist once yer knew who he wuz.”

Angel above, Red knew about his friendship with his own Grillby from the soulbond. 

The skeleton curled his fingers tighter, “i’m tired of waitin’ on yer to come home an’ apologize.” Why the fuck would he apologize to his...his...his rapist?! “it’s a lotta effort followin’ yer ‘round, makin’ sure whatever rat hole yer sleep in aint infested with scavengers, and yer not a lick grateful. gotta say, that machine yer building, it looks awful similar to one ‘dings made ‘fore he decided to take a swim in the core.” 

“w-what? i don’t know what you’re talking about.” 

Red chuckled, “cute, sweetheart, real cute. thinkin’ yer can lie or hide from me. i’ve known wut yer been up this whole time. now yer’ve had yer fun. i’m here to tells yer it’s over.” He was utterly unrepentant. Stalking Sans was simply a fact to him. Not a thing to be ashamed of since it was evident he saw him as a pretty piece of property that made his soul feel nice. “yer mine. i promised i’d take care of yer when i found yer, decided to put a collar on yer and bond us.”

The hand on Sans’ neck shifted, becoming a vice, then suddenly, his skull was slamming into the countertop. “if takin’ care of yer, making sure yer safe means i hafta hurt yer a lil, then i’ll do it. jus’ know that yer the cause of yer own suffering. i don’t want to do this.” Phalanges curled around his own, a thumb pressing against a fragile digit. “i never wanted to hurt yer.” The pressure increased, Sans distantly aware that the bone was about to snap. “and if yer behave, i’ll never hurt yer ‘gain. yer won’t hafta worry ‘bout machines or goin’ hungry or kiddos with knives...”

CRACK!

His voice dropped to a whisper, teeth pressed to his skull like a lover, “jus’ remember. yer don’t have anywhere yer can run that i can’t follow. yer soul wants to be wit mine and it hurts the both of us when yer stubborn.” Red trapped another phalange, Sans helpless to free himself. “i’ll chase yer through time an’ space if i hafta, pet. I’ll chain yer down and break yer body without scratchin’ yer hp.” The sickly possessiveness was back, filled with corrupted affection. “s’all ‘bout the intent. and i can be real gentle if yer let me.”

CRACK!

Scarlet dripped from the fractures and splits like blood. He was literally leaking DT onto the counter. 

“now i’mma give yer one chance to make all this go away. i’ll ferget ‘bout everythin’. yer runnin’ off, yer bitin’ me, yer building that machine. all yer gotta do is apologize fer makin’ me wait and fer makin’ me hurt yer.”

Sans found his ability to speak through the haziness and pain, “If i don’t?”

Red examined his ‘handy-work’, claws smearing runny drops along the slope of Sans’ palm, “then yer will never see the sun ‘gain.” His grip became an iron cuff, “i’ll do what other masters do wit unruly pets. keep yer nice and compliant wit suppressants, chain yer to the fuckin’ wall and snap yer every bone ‘till yer decide to beg fer mercy. and when yer do...i’ll keep breaking them until yer beggin’ fer me to hurt yer more ‘cause yer deserve it. do we have an understandin’?”

The divide lay open ahead of him. Two paths. He could spit in the face of this offer, keep fighting until he was dust...or he could do what he did best, and give up. 

“well, dollface?”

He was tired of running. Tired of fighting. Tired of hurting. Even if he got back to his own timeline, back to his brother, he’d be back in the endless loop of resets unless he found a way to stop the human. A darker possibility arose as he considered the kid having grown bored of playing with the Underground’s inhabitants, and leaving it empty, never to ‘play’ again.

His spiralling thoughts delved into that tiny box shoved into a corner that he tried to ignore for the past month. The one that whispered how he deserved every moment of suffering Red promised. That told him how much of a coward he was, and if he really wanted to hurt to stop, he could have done so a long time ago. He could have fought harder against Red, or even thrown aside his shredded morals and gained LOVE. Then he would have be stronger and have Karma. He could have dusted himself. DT be damned, if his own death was what he wanted, then he could have shattered his own soul and possibly brought Red down with him.

Worthless. Pathetic. Broken. 

“tsk. it’s not that hard a choice when yer stop thinkin’ ‘bout what yer deserve and start thinkin’ ‘bout what yer want.” Red smoothed a hand along the tiny crack along Sans’ skull. “do yer wanna hurt or do yer wanna be happy.”

“...i...i...don’t want to hurt.”

“then yer want me to take care of yer? put yer collar back on and get yer all cleaned up? i’m not too good at healin’ but i dun mind scars. they’ll be a good reminder ‘fore if you think ‘bout misbehaving ‘gain.”

“i…s-so...”

“use yer words, pet.”

“I’m...i’m sorry…”

Red fiddled with the broken fingers, “for?”

“for making you h-hurt me. for running away. for attacking you.” The apology tasted of poison. He deserved this. 

“mhm. see, i’m not real sure if yer mean that. easy to lie wit words.” He gripped an unbroken digit. Sans swallowed the urge to expel the magic churning in his proverbial gut. Weakly, he pawed at the front of Red’s vest, pressing their skulls together in a haphazard attempt at a kiss. He couldn’t form a tongue but Red didn’t seem to mind. The other skeleton ceased toying with mangled digits to shove his tongue past Sans’ teeth, his soul singing in triumph. It was a long, noisy assault on his mouth, hardly deserving of the word kiss. 

Sans shivered.

He was cold. 

Tired and numb and cold.

Red pulled away, rubbing Sans’ bare throat, “yer made the right choice. now how ‘bout you take a nap. it’s been a long month.” He gathered Sans’ limp form into his arms and carried him out of the bar. Eyes followed them. Silent. Not a single one protesting how Red treated his pet. Another reminder that if he dared escape, there were no allies in this world. He was alone.

“time to go home.”

Sans shut his eyesockets.

_‘i’m just on vacation paps. don’t worry, i’ll see you again someday.’_

**Author's Note:**

> Aaaaand that's all she wrote.
> 
> Thank you for reading. I have a certain fondness for angst/horror stories and decided to mix that with the all too common soulmate trope. Halloween is a perfect time for some dark themes, eh? And if you're wondering what happens next, well, that is up to you reader. Did Sans bide his time and escape? Did he give up entirely? Even if he did escape, what would he do?
> 
> Want to see what else I'm planning to write? Want to see updates or previews of existing stories? Want to suggest prompts? Check out my [tumblr](https://catsitta.tumblr.com/). 
> 
> NOTES (for a couple references you may have missed!):  
> \+ Red's HP wasn't harmed by Sans' Karma.  
> \+ Red's LV is 7 to match the number of human souls collected to break the barrier.  
> \+ Sans' thoughts in the first portion of the story are a direct reference to the Post-Leaderless Ending phone call, where he mentions that this is what happens when people like him do nothing.  
> \+ There is no machine in Red's basement  
> \+ The reason why Sans feels Red's intent more intensely than what his LV warrants is related their being soulmates  
> \+ Sans is responsible for that second gold tooth—ie, the window incident  
> \+ There was never an Underfell Genocide Run  
> \+ The ending line is a reference to the King Papyrus Ending, where Sans tells him that all his friends are on vacation instead of dead.


End file.
